Aromatic L-amino acid decarboxylase (AADCD) deficiency is an autosomal recessive neurometabolic disorder, caused by biallelic mutations in the DDC gene, that impairs the synthesis or metabolism of neurotransmitters leading to severe motor dysfunction. The main clinical signs are oculogyric crisis, hypotonia, hypokinesia, and dystonia. The biochemical diagnosis can be performed in cerebrospinal fluid by neurotransmitter analysis, which requires an invasive lumbar puncture, and the sample needs to be shipped frozen to a reference laboratory, usually across a country border. Measurement of AADC activity in plasma is also possible, but available in a few labs globally. 3-O-methyldopa (3-OMD) is a catabolic product of L-dopa and it is elevated in patients with AADC deficiency. The quantification of 3-OMD can be performed in dried blood spots (DBS), a sample that could be shipped at room temperature. 3-OMD levels of AADCD patients and controls were quantified in DBS by liquid chromatography tandem mass spectrometry. DBS samples from 7 Brazilian patients previously diagnosed with AADCD were used to validate the 3-OMD quantification as a screening procedure for this condition. All AADCD patients had at least a four-fold increase of 3-OMD. Thus, 3-OMD seems to be a reliable marker for AADCD, with potential use also in the newborn screening of this disease.

芳香族L-氨基酸脱羧酶（AADCD）缺乏症是由DDC基因中的双等位基因突变引起的常染色体隐性神经代谢紊乱，损害神经递质的合成或代谢，导致严重的运动功能障碍。主要的临床体征是眼科危象，肌张力减退，运动减退和肌张力障碍。可以通过神经递质分析在脑脊液中进行生化诊断，这需要进行有创的腰椎穿刺，并且通常需要将样品冷冻运送到参考实验室，通常跨越一个国家边界。也可以测量血浆中AADC的活性，但是在全球的一些实验室中都可以使用。3- Ø-甲基多巴（3-OMD）是L-多巴的分解代谢产物，在AADC缺乏症患者中升高。3-OMD的定量可以在干血斑（DBS）中进行，干血斑可以在室温下运输。通过液相色谱串联质谱法在DBS中量化AADCD患者和对照的3-OMD水平。来自7名先前被诊断出患有AADCD的巴西患者的DBS样本被用于验证3-OMD定量，作为对此疾病的筛查程序。所有AADCD患者的3-OMD至少增加了四倍。因此，3-OMD似乎是AADCD的可靠标志物，在该疾病的新生儿筛查中也有潜在用途。